Sex-specific control of locomotor behavior by neuronal Arhgef10 in aged Drosophila

Mutations and polymorphisms in the Rho guanine nucleotide exchange factor 10 (ARHGEF10) locus are associated with behavioral and locomotor dysfunctions in humans, including psychiatric disorders and polyneuropathies that show age- and sex-specific prevalence. ARHGEF10 encodes a conserved guanine exchange factor that activates Rho GTPases and has proposed roles in cell migration and adhesion, but the relevant cell types and mechanisms underlying its age- and sex-dependent effects remain unclear. Drosophila darhgef10 gene is the single orthologue of vertebrate ARHGEF10 and its paralogue ARHGEF10L. Here, to gain more direct insight into possible age- and sex-dependent ARHGEF10 neuromuscular functions, we generated darhgef10 knock-out flies and quantified induced walking kinematics with high-speed imaging and coarse spontaneous behaviors--walking, micromovements, rest, and sleep--in open arenas. Mutants of both sexes exhibited abnormal walking kinematics, which worsened with age in females. Cell-type-specific knockdowns indicated that locomotor phenotypes arose primarily from neuronal, rather than glial or muscle, requirements. dArhgef10 was especially critical in glutamatergic motor neurons of aged females. dArhgef10 was also required for wakefulness and activity initiation in females but, surprisingly, not in males. Genetic rescue and isoform expression analyses suggested that sexually-dimorphic expression of long isoforms RC and/or RD underlies at least part of the sex-specific requirements of dArhgef10 in locomotor behavior control, revealing unanticipated complexity in its activity regulation. Collectively, our results suggest ARHGEF10 plays an ancient, conserved role in neurons that promotes proper wakefulness and locomotor activity in an age- and sex-dependent manner.